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Impact of region-of-interest method on quantitative analysis of DTI data in the optic tracts.

Lilja Y, Gustafsson O, Ljungberg M, Nilsson D, Starck G - BMC Med Imaging (2016)

Bottom Line: ROI selection in small structures is challenging; the final measurement results could be affected due to the significant impact of small geometrical errors.Manual tracing was performed in 1) the b0 image and 2) a T1-weighted image registered to the FA image.Semi-automatic segmentation was performed based on 3) tractography and 4) the FA-skeleton algorithm in the tract-based spatial statistics (TBSS) framework.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. ylva.lilja@neuro.gu.se.

ABSTRACT

Background: To extract DTI parameters from a specific structure, a region of interest (ROI) must be defined. ROI selection in small structures is challenging; the final measurement results could be affected due to the significant impact of small geometrical errors. In this study the optic tracts were analyzed with the aim to assess differences in DTI parameters due to ROI method and to identify the most reliable method.

Methods: Images of 20 healthy subjects were acquired. Fractional anisotropy (FA) was extracted from the optic tracts by four different ROI methods. Manual tracing was performed in 1) the b0 image and 2) a T1-weighted image registered to the FA image. Semi-automatic segmentation was performed based on 3) tractography and 4) the FA-skeleton algorithm in the tract-based spatial statistics (TBSS) framework. Results were analyzed with regard to ROI method as well as to inter-scan, intra-rater and inter-rater reliability.

Results: The resulting FA values divided the ROI methods into two groups that differed significantly: 1) the FA-skeleton and the b0 methods showed higher FA values compared to 2) the tractography and the T1-weighted methods. The intra- and inter-rater variabilities were similar for all methods, except for the tractography method where the inter-rater variability was higher. The FA-skeleton method had a better reproducibility than the other methods.

Conclusion: Choice of ROI method was found to be highly influential on FA values when the optic tracts were analyzed. The FA-skeleton method performed the best, yielding low variability and high repeatability.

No MeSH data available.


Illustration of the four ROI methods (upper row: axial slices of whole MRI images; lower row: close-ups of the optic tracts and ROIs). From the left: a manual ROI in b0 image, b manual ROI in coregistered T1-weighted image, c ROI guided by FA-skeleton (FA-skeleton in green) and d ROI guided by probabilistic tractography. The pink lines in the tractography image represent the termination masks of the tractography. A complete ROI cannot be shown in a single axial slice as the optic tracts are oriented anatomically in an inferior-superior direction, thus only parts of the ROIs are seen in this image (indicated as red or blue voxels)
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Fig3: Illustration of the four ROI methods (upper row: axial slices of whole MRI images; lower row: close-ups of the optic tracts and ROIs). From the left: a manual ROI in b0 image, b manual ROI in coregistered T1-weighted image, c ROI guided by FA-skeleton (FA-skeleton in green) and d ROI guided by probabilistic tractography. The pink lines in the tractography image represent the termination masks of the tractography. A complete ROI cannot be shown in a single axial slice as the optic tracts are oriented anatomically in an inferior-superior direction, thus only parts of the ROIs are seen in this image (indicated as red or blue voxels)

Mentions: ROIs were defined manually by visual inspection of the b = 0 map. The two most central voxels of the OT, in each coronal slice, were selected (Fig. 3).Fig. 3


Impact of region-of-interest method on quantitative analysis of DTI data in the optic tracts.

Lilja Y, Gustafsson O, Ljungberg M, Nilsson D, Starck G - BMC Med Imaging (2016)

Illustration of the four ROI methods (upper row: axial slices of whole MRI images; lower row: close-ups of the optic tracts and ROIs). From the left: a manual ROI in b0 image, b manual ROI in coregistered T1-weighted image, c ROI guided by FA-skeleton (FA-skeleton in green) and d ROI guided by probabilistic tractography. The pink lines in the tractography image represent the termination masks of the tractography. A complete ROI cannot be shown in a single axial slice as the optic tracts are oriented anatomically in an inferior-superior direction, thus only parts of the ROIs are seen in this image (indicated as red or blue voxels)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4940685&req=5

Fig3: Illustration of the four ROI methods (upper row: axial slices of whole MRI images; lower row: close-ups of the optic tracts and ROIs). From the left: a manual ROI in b0 image, b manual ROI in coregistered T1-weighted image, c ROI guided by FA-skeleton (FA-skeleton in green) and d ROI guided by probabilistic tractography. The pink lines in the tractography image represent the termination masks of the tractography. A complete ROI cannot be shown in a single axial slice as the optic tracts are oriented anatomically in an inferior-superior direction, thus only parts of the ROIs are seen in this image (indicated as red or blue voxels)
Mentions: ROIs were defined manually by visual inspection of the b = 0 map. The two most central voxels of the OT, in each coronal slice, were selected (Fig. 3).Fig. 3

Bottom Line: ROI selection in small structures is challenging; the final measurement results could be affected due to the significant impact of small geometrical errors.Manual tracing was performed in 1) the b0 image and 2) a T1-weighted image registered to the FA image.Semi-automatic segmentation was performed based on 3) tractography and 4) the FA-skeleton algorithm in the tract-based spatial statistics (TBSS) framework.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. ylva.lilja@neuro.gu.se.

ABSTRACT

Background: To extract DTI parameters from a specific structure, a region of interest (ROI) must be defined. ROI selection in small structures is challenging; the final measurement results could be affected due to the significant impact of small geometrical errors. In this study the optic tracts were analyzed with the aim to assess differences in DTI parameters due to ROI method and to identify the most reliable method.

Methods: Images of 20 healthy subjects were acquired. Fractional anisotropy (FA) was extracted from the optic tracts by four different ROI methods. Manual tracing was performed in 1) the b0 image and 2) a T1-weighted image registered to the FA image. Semi-automatic segmentation was performed based on 3) tractography and 4) the FA-skeleton algorithm in the tract-based spatial statistics (TBSS) framework. Results were analyzed with regard to ROI method as well as to inter-scan, intra-rater and inter-rater reliability.

Results: The resulting FA values divided the ROI methods into two groups that differed significantly: 1) the FA-skeleton and the b0 methods showed higher FA values compared to 2) the tractography and the T1-weighted methods. The intra- and inter-rater variabilities were similar for all methods, except for the tractography method where the inter-rater variability was higher. The FA-skeleton method had a better reproducibility than the other methods.

Conclusion: Choice of ROI method was found to be highly influential on FA values when the optic tracts were analyzed. The FA-skeleton method performed the best, yielding low variability and high repeatability.

No MeSH data available.